Figures are illustrative only, ignore charges and tax, and are not a forecast or personal recommendation.
A savings calculator answers a simple but important question: if I start with a certain amount, add to it regularly, and earn a given interest rate, what will I have at the end of the term? The tool above does exactly this, using monthly compounding on both your initial balance and your ongoing deposits, and separates the total into what you actually paid in versus what was earned as interest.
How to use it
Enter your current savings balance, how much you plan to add each month, the interest rate you expect to earn (check your provider's current rate, since savings rates move with the Bank of England base rate and provider pricing), and the number of years you plan to save for. The projected pot, total paid in, and interest earned update instantly as you adjust any figure.
Cash savings vs investing
This calculator works equally well for a cash savings account or, with the caveat that returns are never guaranteed, as a simple projection for investing. The key practical difference is reliability: a bank or building society savings rate is fixed for the period stated (or variable but published), whereas an investment return is an assumption based on historical long-run averages that could easily be higher or lower in any given year. If you're trying to decide between the two approaches for the same pot of money, our Savings vs Investment Calculator runs both scenarios side by side so you can see the gap in outcomes.
Worked example
Starting with £5,000, adding £150 a month, at 4% a year, over 10 years produces a healthily larger pot than the £23,000 paid in — with the exact difference driven by how consistently the 4% compounds. Extend the term to 20 years in the calculator and you'll see the interest component roughly triples in importance relative to the principal, which is the essence of why starting early matters more than most people initially assume.
Should this money go in an ISA?
If you're saving cash, a Cash ISA shelters the interest from tax, which matters more the larger your balance and the higher rates are. Many savers default to cash without considering that, over long time horizons, inflation quietly erodes cash returns in a way that a Stocks & Shares ISA, taken over many years, has historically outpaced — though with more volatility along the way. If you're weighing up ISA options more broadly, our ISA Calculator projects a Stocks & Shares ISA specifically, using annual contribution amounts in line with how many people actually fund an ISA.
Frequently asked questions
Does the interest rate stay the same for the whole term?
The calculator assumes a single constant rate for simplicity. In reality, easy-access savings rates can change at any time, and even fixed-rate products only guarantee the rate for their stated term, after which the rate typically reverts to a variable one.
Is interest paid monthly in real accounts?
Some accounts pay interest monthly, others annually or at maturity — this affects exactly how compounding happens in practice, though the difference in outcome over long periods is usually modest. This tool assumes monthly compounding as a reasonable general approximation.
What's a realistic savings rate to use?
This varies with the wider interest rate environment. Rather than guessing, it's worth checking current best-buy tables for easy-access, notice, and fixed-term savings accounts before relying on the projection for real planning.
How is this different from the Compound Interest Calculator?
They use the same underlying maths — our Compound Interest Calculator is aimed at illustrating the mechanics of compounding generally, while this one is framed specifically around planning a savings goal.
Should I keep an emergency fund in this account?
Money you might need at short notice is generally better kept in an easy-access account rather than tied up for growth, regardless of what a longer-term projection like this one shows.
Common mistakes when projecting savings
A frequent mistake is assuming an introductory or promotional savings rate will apply for the whole projection period, when in reality many easy-access accounts offer a bonus rate for the first 12 months only, reverting to a lower standard rate afterwards. If your account works this way, it's more realistic to run the projection using the standard ongoing rate, or to break the projection into two shorter periods at the two different rates and add the results together.
Another mistake is failing to compare the account against inflation before committing to a long-term savings plan. A savings rate that looks attractive in isolation can still leave you losing purchasing power in real terms if inflation runs higher, which is easy to miss when only looking at the nominal pot size growing over time. It's worth pairing this calculator with our Inflation Erosion Calculator before assuming a savings plan alone is enough for a long-term goal.
What's the difference between AER and gross rate?
AER (Annual Equivalent Rate) shows what the rate would be if interest were compounded and paid annually, making it the standard figure for comparing accounts regardless of how often they actually pay interest — always compare AER to AER, not gross monthly rates to annual ones.
Should I split savings across multiple accounts?
This can make sense to stay within Financial Services Compensation Scheme (FSCS) protection limits per banking institution, or to combine a notice account's higher rate with an easy-access account's flexibility — the projection above works the same whether it represents one account or a combined total across several.
Does it matter which bank or building society I choose?
Beyond the headline rate, it's worth checking whether the provider is covered by the UK's Financial Services Compensation Scheme (protecting up to £85,000 per person, per institution, as of the 2025/26 scheme limit), how easily you can access the money, and whether the rate is fixed or variable, since a variable rate can change at any time regardless of what's entered in this projection.
Is it worth switching savings accounts for a slightly better rate?
For larger balances held over several years, even a modest rate improvement compounds into a meaningful extra amount, as this calculator illustrates — for small balances or very short time horizons, the effort of switching may outweigh the benefit, so it's worth weighing the pot size and remaining term before assuming switching is automatically worthwhile.